1. Field of the Invention
The present invention relates to a simulator for simulating an object to be controlled, such as a manufacturing plant or the like, and a controlling unit. More particularly, the present invention relates to a simulator for reproducing operations to be performed by a real object or machine at a higher accuracy.
2. Description of the Related Art
A simulator is used for simulating operations to be performed by a large-sized machine when it is designed and adjusted, when various kinds of processes are researched and tested, or when an operator is trained on dangerous or difficult machines.
To facilitate understanding of the present invention, a typical example of a conventional simulator will be described below with reference to FIG. 1, wherein it is assumed that the simulator is used for a water supply control process in a power station.
FIG. 1 is a block diagram of the conventional simulator for a water supply control process.
An output from a controlling unit 10 is input into a simulator 20. The controlling unit 10 is constructed of a comparing/calculating circuit 11 and a processing/calculating circuit 12. As is apparent from the drawing, a target value a of an object to be controlled and an output from the simulator 20 are input into the comparing/calculating circuit 11. In response to the input signals, the comparing/calculating circuit 11 calculates a differential control signal f. This differential control signal f is specifically processed in the processing/calculating circuit 12, and thereafter, it is input into the simulator 20 in the form of a processed quantity g.
FIG. 2 is a block diagram that schematically shows the structure of the simulator 20, particularly illustrating a simulation of the same.
As shown in the drawing, the simulator 20 has processing delay characteristic 21, pump delay characteristic 22 and pump rotational speed vs discharge flow rate characteristic 23. A simulation control quantity d is calculated in the simulator 20 based on the process quantity g, and thereafter, it is output from the simulator 20.
When a modelled simulator as described above is used, an output signal from the controlling unit 10 is input to the simulator 20 in the form of a process quantity g. The controlling unit 10 operates to cause the simulation control quantity d fed back from the simulator 20 to coincide with the target value a. Each object to be controlled by the simulator 20 is modelled with respect to the processing delay characteristic 21, the pump delay characteristic 22 and the pump rotational speed vs. discharge flow rate characteristic 23. Thus, properties of the resultant model are previously determined before a real machine is designed.
In practice, however, the simulator 20 does not completely simulate the properties of the real machine. Thus, there often arises a malfunction that the properties of each model do not coincide with those of the real machine when water supply control is simulated with the aid of the controlling unit 10 and the simulator 20.
For example, when a plant is controlled, each actuator has not only delay but also back-lash. Moreover, there arises a problem that properties of the actuator in the opening direction differ from those in the closing direction. Further, since pump properties of the model do not completely coincide with those of the real machine, there arises another problem that a flow rate of supply water of the model differs from that of the real machine.
FIG. 3 is a graph which shows characteristic curves representing pump NQ characteristics, particularly illustrating a difference between designed values and practically measured values. In the drawing, a characteristic curve A represents designed values and a characteristic curve B represents practically measured values.
It is apparent from the drawing that the designed values of the pump NQ characteristics differ considerably from the practically measured values of the same. Due to the difference as mentioned above, the simulator 20 cannot completely simulate the real machine.
Thus, in an operation training simulator in which operations of a controlling unit are performed with the aid of a simulation circuit or a software that merely attempt to duplicate an operation panel of a model each operation training cannot be achieved correctly.